docs: def _get_backend(name: str = None):
      """Get a plotting backend.
  
      Tries to get it using the name - or the default one.
      """
      if not backends:
          raise RuntimeError("No plotting backend available. Please, install matplotlib (preferred) or bokeh (limited).")
      if not name:
          name = _default_backend
      if name == "bokeh":
          raise RuntimeError("Support for bokeh has been discontinued. At some point, we may return to support holoviews.")
      backend = backends.get(name)
      if not backend:
          raise RuntimeError("Backend {0} does not exist. Use one of the following: {1}".format(name, ", ".join(backends.keys())))
      return name, backends[name]